Revenue Recognition - Summary of Deferred Revenue Activity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Movement in Deferred Revenue [Roll Forward]
Deferred revenue balance, beginning of period	$ 57.8	$ 59.0	$ 51.9
New deferrals	200.6	252.0	335.6
Amounts recognized in revenue	(191.0)	(253.2)	(328.5)
Deferred revenue balance, end of period	$ 67.4	$ 57.8	$ 59.0